Bovine Tissue Factor has been purified to homogeneity. Specific antigens against bovine tissue factor has been prepared and will be used to look for expression of tissue factor in cultured bovine cells under a number of conditions. The purified bovine tissue factor will be used to study its role in the initiation of coagulation. Specific protein inhibitors of bovine tissue factor have been found in bovine plasma. We plan to isolate and characterize these inhibitors. We are in the process of purifying human tissue factor. When a pure preparation is obtained we will use it to prepare specific antisera. Having anti-tissue factor antibodies will enable us to study the release of tissue factor into the plasma directly during the course of diseases associated with hypercoagulability.